The subject matter disclosed herein relates generally to solar power generation systems and more particularly to frequency control of solar power generation systems.
Traditional power generation equipment (such as synchronous generators) naturally responds to frequency disturbances due to the grid coupled rotating inertia and governor controls of such equipment. Solar power generation equipment presently does not have the frequency-regulating capability of synchronous generators.
Solar power generation systems have photovoltaic (PV) modules, which produce electrical power. In order to feed the electrical power to the grid, power electronic elements are used for power conditioning. In one example, the power electronic elements include a direct current (DC) to DC converter and a DC to alternating current (AC) inverter connected back to back through a DC link.
As new grid codes are developed for solar power generation systems, and as market penetration level of solar power increases, variability of solar power is becoming less acceptable to utility companies. For example, utility companies are imposing or expected to impose requirements related to power ramp rate limits, curtailment, and frequency stabilization.
Frequency stabilization relates to stabilizing the grid frequency. It is a well-known characteristic of utility systems that the grid frequency tends to decrease when the load exceeds the generation and to increase when the generation exceeds the load. Such decreases or increases may occur in a monotonic manner, an oscillating manner, or combinations thereof when the grid is subjected to a sudden change in the balance between generation and load. It is a consideration in the design of such a system that any method to achieve compensation of such decreases or increases should be one that does not result into aggravating the grid oscillations.
It would be desirable to enable solar power generation systems to provide frequency stabilization capability in order to increase the stability and reliability of the power grid to which the system is coupled.